1. Field of the Invention
The present invention relates to an art of measuring colors by means of a calorimeter and an art of printing based on profiles obtained thereby.
2. Description of the Related Art
The colorimeter is used to measure correctly the color of outputs by an output device, for example, the color of prints and outputs of a display. JP-A-10-142775 is an example of related art.
So far, the colorimetric values resulting from the measurement of colors by means of a colorimeter have been used on the assumption that such calorimetric values are correct. For example, a color conversion table is used to output desired colors on a printing device, and for the preparation of this color conversion table, the colorimeter is used. In other words, with regard to the color gradation value in instrument-dependent color spaces, for example, the color gradation value for which the amount of recording materials used is specified for each color in a printing device, actual output must be made based on this color gradation value to specify colors.
Therefore, actually the required number of patches are printed, and their colors are measured by means of a calorimeter to obtain a calorimetric value, and this calorimetric value is used to correlate the color gradation value in the instrument-independent color spaces and the color gradation value for each color of the recording material mentioned above constituting thus a color conversion table. Here, in the calorimeter, the observation conditions are specified for measuring the colors of the patches, and any calorimetric value is correct as far as these observation conditions are assumed. However, nobody can say that this calorimetric value is correct even under different observation conditions. In other words, the result of conversion based on this color conversion table is strictly correct only when the print is observed under the same observation conditions as that for the calorimeter.
It is only natural that the colorimetric value differs when observation conditions are different. However, when the colorimetric value is largely different between the observation condition under which the object of color measurement is measured by a calorimeter and the observation condition existing in the environment when the object of color measurement is actually is used, there will be problems when the object of color measurement is actually used. In other words, when the observation conditions serving as the basis for making a color conversion table and the observation conditions under which the observer observes the print are different, the observer may feel that the color is different from the color intended by the author when he or she made the color conversion table mentioned above. For example, the observer may feel that color contrast is weaker than that intended by the author, or the observer may feel that the print has a hue different from the color intended by the author. Particularly with regards to outputs whose color appearance tends to be different due to difference in observation conditions, for example, with regards to outputs printed by pigment ink, the above problem tends to occur.
And although it is preferable that a calorimeter be available for measuring colors under the observation conditions for observing actually the object of color measurement, the use of such a calorimeter for measuring the color of a large number of objects of color measurement is often inconvenient. In other words, there are two types of color measurement devices. One is a color measurement device capable of automatically measuring a plurality of objects of color measurement and the other is one capable of measuring the color of a plurality of objects of color measurement by changing the object of color measurement by manual operation. The former operates in the state wherein observation conditions have been determined in advance, while the latter involves the discretion of the operator vis-a-vis the choice of observation conditions.
However, in the case of color measurement for various uses by making the above-mentioned color conversion table, however, it is almost indispensable to measure color automatically. In other words, it is necessary to measure the color of a large number (for example 1,000) patches in order to make a color conversion table. However, it is unrealistic to measure one by one the color of such a large number of patches by manual operation, and their automatic measurement is almost indispensable. Therefore, in the past, it has been difficult to acquire correct calorimetric values when a large number of objects of color measurement are observed under a required observation condition.